Dale,
I could have shown you what I did to my G 18 at R2K1 but I didn't know you were having a problem. Ron Larson and I came up with almost the same solution at almost the same time.
The skeg(which we both hot glued on to start with) is about 20" long, no more than 1" wide at the aft most part tapering to 0" at the front.1/4 to 5/16" thick. The skeg is installed so the back of it is where the stern stem really starts to rise. It sort of extends the keel, if a G has a keel.
Mine is about 3/4" wide and 20" long,1/4" thick, works great, did not affect the G's manuverability, is less likely to be damaged because it is not the lowest part of the boat. Lets her track as if on rails.
Ray